Fastener having adjustable fastening strength

ABSTRACT

Clothlike materials may become abraded upon disengagement of mechanical fasteners. This abrasion may cause a decrease in aesthetic appeal, as well as a decrease in functionality of attachment systems. As a result, there has remained a need for improved fastening systems. Moreover, there has remained a need for improved fastening systems for disposable absorbent articles.

BACKGROUND

The present invention relates to improved fastening systems. More particularly, the present invention relates to improved hook and loop fastening systems for disposable absorbent articles.

Conventional disposable absorbent articles, such as disposable diapers, have typically included a bodyside liner, an outer cover, and an absorbent core located between the outer cover and the bodyside liner. The disposable absorbent articles have generally defined a front region, a rear region, and a crotch region which extends between and connects the front and rear regions. Such conventional disposable absorbent articles have also included fastening systems which are configured to secure the article on the wearer's waist. The disposable absorbent articles have also been constructed with various types of elasticized portions at the waist and leg opening regions. Such elasticized portions have been used to reduce the leakage of body exudates from the disposable absorbent article and improve the appearance and fit of the article about the wearer.

Typically, the fastening systems on conventional disposable absorbent articles have included a pair of fasteners located on the outermost corners of the article in one of the waist regions. Such fasteners have been configured to releasably engage a complimentary fastener in the opposite waist region of the disposable absorbent article. For example, the fastening systems have included a pair of mechanical fasteners, such as hook material, located on the outermost corners of the disposable absorbent article in the rear region of the article. Such systems have also included a complimentary fastener, such as a loop material panel, located on the outer surface of the outer cover of the disposable absorbent article in the front region of the article. In such a configuration, the disposable absorbent article has been positioned between the legs of the wearer and the hook material has been releasably attached to the loop material panel to secure the article about the waist of the wearer. In some disposable absorbent articles the loop material panel has been removed and the hook material has been releasably attached to the outer cover of the diaper. This is known as a fasten anywhere configuration.

However, conventional disposable absorbent articles which are configured as described above have exhibited several shortcomings. For example, with the desire for disposable absorbent articles to be more clothlike, manufacturers have made the outer cover and the loop material increasingly fluffier, softer, and correspondingly more susceptible to abrasion. As a result, these clothlike materials become abraded upon disengagement of the mechanical fasteners. This abrasion may cause a decrease in aesthetic appeal, as well as a decrease in functionality of the attachment system.

As a result, there has remained a need for improved fastening systems. Moreover, there has remained a need for improved fastening systems for disposable absorbent articles.

SUMMARY

The present inventors undertook intensive research and development efforts concerning improving fastening systems. The present invention is directed in part to a fastening system suitable for incorporation into a disposable absorbent article. The fastening system may include a female component; and a male component having a plurality of hook elements adapted for releasable engagement with the female component. Further, the fastening system has a first normalized peak shear force to disengage the female component from the male component when the male component is stretched 0%. The fastening system also has a second normalized peak shear force to disengage the female component from the male component when the male component is stretched 10%. The first normalized peak shear force is at least 10% greater than the second normalized peak shear force.

Another aspect of the present invention is directed to a fastening system suitable for incorporation into a disposable absorbent article. The fastening system may include a female component; and a male component having a plurality of hook elements adapted for releasable engagement with the female component. At least a portion of the plurality of hook elements have a stem and a cap, and the cap defines a cap angle. Further, the fastening system has a first normalized peak shear force to disengage the female component from the male component and a first average cap angle when the male component is stretched 0%. The fastening system has a second normalized peak shear force to disengage the female component from the male component and a second average cap angle when the male component is stretched 10%. The first normalized peak shear force is greater than the second normalized peak shear force, and the second average cap angle is greater than the first average cap angle.

Another aspect of the present invention is directed to a fastening system suitable for incorporation into a disposable absorbent article. The fastening system may include a female component; and a male component having a plurality of hook elements adapted for releasable engagement with the female component. Further, the fastening system has a first normalized peak shear force to disengage the female component from the male component when the male component is stretched 0%. The fastening system has a second normalized peak shear force to disengage the female component from the male component when the male component is stretched 10%. Further, the first normalized peak shear force being at least 10% less than the second normalized peak shear force.

Another aspect of the present invention is directed to a fastening system suitable for incorporation into a disposable absorbent article. The fastening system may include a female component; and a male component having a plurality of hook elements adapted for releasable engagement with the female component. At least a portion of the plurality of hook elements have a stem and a cap, the cap defining a cap angle. The fastening system having a first normalized peak shear force to disengage the female component from the male component and a first average cap angle when the male component is stretched 0%. The fastening system having a second normalized peak shear force to disengage the female component from the male component and a second average cap angle when the male component is stretched 10%. The first normalized peak shear force being less than the second normalized peak shear force, and the second average cap angle being less than the first average cap angle.

DRAWINGS

The foregoing and other features, aspects and advantages of the present invention will become better understood with regard to the following description, appended claims and accompanying drawings where:

FIG. 1 illustrates a plan view of a disposable absorbent article in an unfolded, flat-out, uncontracted state (i.e., with all elastic induced gathering and contraction removed), with the bodyfacing surface of the article facing the viewer and with portions of the article partially cut away to illustrate underlying features;

FIG. 2 illustrates a plan view of a disposable absorbent article in an unfolded, flat-out, uncontracted state, with the garment facing surface of the article facing the viewer and with portions of the article partially cut away to illustrate underlying features;

FIG. 3A illustrates a side view of a first hook material;

FIG. 3B illustrates a side view of the hook material of FIG. 3A while extended;

FIG. 4A illustrates a side view of a second hook material;

FIG. 4B illustrates a side view of the hook material of FIG. 4A while extended;

FIG. 5A illustrates a side view of a third hook material;

FIG. 5B illustrates a side view of the hook material of FIG. 5A while extended;

FIG. 6A illustrates a side view of a fourth hook material;

FIG. 6B illustrates a side view of the hook material of FIG. 6A while extended; and

FIG. 7 illustrates a representative test sample.

DESCRIPTION

The present invention relates to improved fasteners and improved fasteners for use in disposable absorbent articles. As used herein, the term “disposable” refers to articles which are intended to be discarded after a limited use and which are not intended to be laundered or otherwise restored for reuse. The disposable absorbent articles of the present invention will be described in terms of a disposable diaper which is adapted to be worn by infants about the lower torso. It is understood that the improved fastening system of the present invention is equally adaptable for use with other types of disposable absorbent articles such as adult incontinence garments, children's training pants, surgical gowns and the like.

With regard to the designated surfaces of a disposable absorbent article and its components, the various upper or bodyfacing surfaces are configured to face toward the body of the wearer when the disposable absorbent article is worn by the wearer for ordinary use. The various opposing, lower, or garment facing surfaces are configured to face away from the wearer's body when the disposable absorbent article is worn by the wearer.

As used herein, reference to two materials or elements being “joined” is intended to refer to the situation wherein the two materials or elements are directly joined to one another, where they are indirectly joined to one another, or where they are indirectly joined to an intermediate element. Similarly, methods of joining two materials or elements include forming the elements or materials integrally, attaching the elements together such as through the use of adhesive bonds, sonic bonds, thermal bonds, pinning, or stitching, or a variety of other attachment techniques known in the art, as well as combinations thereof.

“Stretchable” refers to materials which are either elastic or extensible, that is materials which when elongated in one or more dimensions either exert a force tending to move the material at least partially to its original dimensions (elastic), or which remain in the elongated configuration (extensible).

It should be noted that the stretch, elastic or extensible properties of a stretchable material are determined when the material is dry. Additionally, the percentage of elongation, extension, or permanent deformation can be determined in accordance with the following formula:

100*[(L-L_(o))/(L_(o))]

-   -   where: L=elongated length; and         -   L_(o)=initial length.

Referring now to the drawings, FIG. 1 illustrates a disposable absorbent article such as a disposable diaper (30) in an unfolded, flat-out, uncontracted state (i.e., with all elastic induced gathering and contraction removed). Portions of the structure are partially cut away to more clearly show the interior construction of the diaper (30), with the surface of the diaper (30) which contacts the wearer facing the viewer. FIGS. 1 and 2 illustrate a disposable diaper (30) as having a front region (32), a rear region (34) and a crotch portion (36) located between the front and rear regions. The diaper (30) comprises a backsheet (38), a topsheet (40), and an absorbent core (42) situated between the backsheet and the topsheet. The outer edges of the diaper (30) define a periphery (44) with transversely opposed, longitudinally extending side edges (46); longitudinally opposed, transversely extending end edges (48); and a system of elastomeric gathering members, such as a system including leg elastics (50) and waist elastics (52). The longitudinal side edges (46) define the leg openings (54) for the diaper (30), and optionally, are curvilinear and contoured. The transverse end edges (48) are illustrated as straight, but optionally, may be curvilinear. The diaper (30) may also comprise additional components to assist in the acquisition, distribution and storage of bodily waste. For example, the diaper (30) may comprise a transport layer, such as described in U.S. Pat. No. 4,798,603, issued to Meyer et al., or a surge management layer, such as described in European Patent Application Publication No. 0 539 703, published May 5, 1993.

The diaper (30) generally defines a longitudinally extending length dimension (56), and a laterally extending width dimension (58), as representatively illustrated in FIG. 1. The diaper (30) may have any desired shape, such as rectangular, I-shaped, a generally hourglass shape, or a T-shape.

The backsheet (38) defines a length and a width which, in the illustrated version, coincide with the length and width of the diaper (30). The absorbent core (42) generally defines a length and width which are less than the length and width of the backsheet (38), respectively. Thus, marginal portions of the diaper (30), such as marginal sections of the backsheet (38), may extend past the transversely opposed, longitudinally extending terminal side edges (60) and/or the longitudinally opposed, transversely extending terminal end edges (62) of the absorbent core (42) to form side margins (64) and end margins (66) of the diaper (30). The topsheet (40) is generally coextensive with the backsheet (38), but may optionally cover an area which is larger or smaller than the area of the backsheet, as desired. The backsheet (38) and topsheet (40) are intended to face the garment and body of the wearer, respectively, while in use. As used herein when describing the topsheet (40) in relation to the backsheet (38) and vice versa, the term “associated” encompasses configurations in which the topsheet is directly joined to the backsheet, and configurations where the topsheet is indirectly joined to the backsheet by affixing portions of the topsheet to intermediate members which in turn are affixed to at least portions of the backsheet. The topsheet (40) and the backsheet (38) can, for example, be joined to each other in at least a portion of the diaper periphery (44) by attachment mechanisms (not shown) such as adhesive bonds, sonic bonds, thermal bonds, pinning, stitching, or a variety of other attachment techniques known in the art, as well as combinations thereof.

The topsheet (40) suitably presents a bodyfacing surface which is compliant, soft feeling, and non-irritating to the wearer's skin. Further, the topsheet (40) may be less hydrophilic than the absorbent core (42), to present a relatively dry surface to the wearer, and is sufficiently porous to be liquid permeable, permitting liquid to readily penetrate through its thickness. A suitable topsheet (40) may be manufactured from a wide selection of web materials, such as porous foams, reticulated foams, apertured plastic films, natural fibers, synthetic fibers (for example, polyester or polypropylene fibers), or a combination of natural and synthetic fibers. The topsheet (40) is suitably employed to help isolate the wearer's skin from liquids held in the absorbent core (42).

Various woven and nonwoven fabrics may be used for the topsheet (40). For example, the topsheet (40) may be composed of a meltblown or spunbonded web of polyolefin fibers. The topsheet (40) may also be a bonded-carded web composed of natural and/or synthetic fibers. The topsheet (40) may be composed of a substantially hydrophobic material and the hydrophobic material may, optionally, be treated with a surfactant, or otherwise processed, to impart a desired level of wettability and hydrophilicity. Specifically, the topsheet (40) may be a nonwoven, spunbond, polypropylene fabric composed of about 2.8 to about 3.2 denier fibers formed into a web having a basis weight of about 22 gsm and a density of about 0.06 g/cc.

The topsheet (40) may also be surface treated with about 0.3 weight percent of a surfactant mixture that contains a mixture of AHCOVEL Base N-62 surfactant and GLUCOPON 220UP surfactant in about a 3:1 ratio based on a total weight of the surfactant mixture. The AHCOVEL Base N-62 surfactant is purchased from Hodgson Textile Chemicals Inc., a business having offices in Mount Holly, N.C., and comprises a blend of hydrogenated ethoxylated castor oil and sorbitan monooleate in a 55:45 weight ratio. The GLUCOPON 220UP surfactant is purchased from Henkel Corporation, Gulph Mills, Pa., and comprises alkyl polyglycoside. The surfactant may also include additional ingredients such as aloe. The surfactant may be applied by any conventional means, such as spraying, printing, brush coating, foam or the like. The surfactant may be applied to the entire topsheet (40) or may be selectively applied to particular sections of the topsheet, such as the medial section along the longitudinal centerline of a diaper, to provide greater wettability of such sections.

The backsheet (38) may suitably be composed of a material which is either liquid permeable or liquid impermeable. It is generally desirable that the backsheet (38) be formed from a material which is substantially liquid impermeable. For example, a typical backsheet (38) can be manufactured from a thin plastic film or other flexible liquid impermeable material. Moreover, the backsheet (38) may be formed from a polyethylene film having a thickness of from about 0.012 mm (0.5 mil) to about 0.051 mm (2.0 mils). If desirous of presenting the backsheet (38) with a more cloth-like feel, the backsheet may comprise a polyethylene film having laminated to the lower or opposing surface thereof a nonwoven web, such as a spunbond web of polyolefin fibers. For example, a polyethylene film having a thickness of about 0.015 mm (0.6 mil) may have thermally laminated thereto a spunbond web of polyolefin fibers, which fibers have a thickness of about 1.5 to about 2.5 denier per filament, which nonwoven web has a basis weight of about 24 gsm (0.7 osy). Methods of forming such cloth-like outer covers are known to those skilled in the art. Further the backsheet (38) may be a stretchable material, a method of forming such a material may be found in U.S. Pat. No. 5,226,992 issued to Morman, further various examples of extensible materials are described in U.S. Pat. No. 6,264,641 issued to VanGompel et al.; the entire disclosures of which are hereby incorporated by reference in a manner that is consistent herewith

Further, the backsheet (38) may be formed of a woven or nonwoven fibrous web layer which has been totally or partially constructed or treated to impart a desired level of liquid impermeability to selected regions that are adjacent or proximate the absorbent core (42). Still further, the backsheet (38) may optionally be composed of micro-porous “breathable” material which permits vapors to escape from the absorbent core (42) while still preventing liquid exudates from passing through the backsheet.

The absorbent core (42) may comprise a matrix of hydrophilic fibers, such as a web of cellulosic fluff, mixed with particles of a high-absorbency material commonly known as superabsorbent material. In a particular version, the absorbent core (42) comprises a mixture of superabsorbent hydrogel-forming particles and wood pulp fluff. The wood pulp fluff may be exchanged with synthetic polymeric, meltblown fibers or with a combination of meltblown fibers and natural fibers. The superabsorbent particles may be substantially homogeneously mixed with the hydrophilic fibers or may be non-uniformly mixed.

The absorbent core (42) may have any of a number of shapes. For example, the absorbent core (42) may be rectangular, I-shaped or T-shaped. It is often considered as desirable for the absorbent core (42) to be narrower in the crotch portion than the rear or front region(s).

The high-absorbency material can be selected from natural, synthetic and modified natural polymers and materials. The high-absorbency materials can be inorganic materials, such as silica gels, or organic compounds, such as crosslinked polymers. The term “crosslinked” refers to any means for effectively rendering normally water-soluble materials substantially water insoluble, but swellable. Such means can comprise, for example, physical entanglement, crystalline domains, covalent bonds, ionic complexes and associations, hydrophilic associations, such as hydrogen bonding, and hydrophobic associations or Van der Waals forces.

Examples of synthetic, polymeric, high-absorbency materials include the alkali metal and ammonium salts of poly(acrylic acid) and poly(methacrylic acid), poly(acrylamides), poly(vinyl ethers), maleic anhydride copolymers with vinyl ethers and alpha-olefins, poly(vinyl pyrolidone), poly(vinyl morpholinone), poly(vinyl alcohol), and mixtures and copolymers thereof. Further polymers suitable for use in the absorbent core include natural and modified natural polymers, such as hydrolyzed acrylonitrile-grafted starch, acrylic acid grafted starch, methyl cellulose, carboxymethyl cellulose, hydroxypropyl cellulose, and the natural gums, such as alginates, xanthum gum, locust bean gum, and the like. Mixtures of natural and wholly or partially synthetic absorbent polymers can also be useful. Processes for preparing synthetic, absorbent gelling polymers are disclosed in U.S. Pat. No. 4,076,663, issued to Masuda et al., and U.S. Pat. No. 4,286,082, issued to Tsubakimoto et al.

The high-absorbency material may be in a variety of geometric forms. It is desired that the high-absorbency material be in the form of discrete particles. However, the high-absorbency material may also be in the form of fibers, flakes, rods, spheres, needles, or the like. Often, the high-absorbency material is present in the absorbent core (42) in an amount of from about 5 to about 100 weight percent based on total weight of the absorbent core.

The disposable absorbent articles described herein also comprise fasteners (82) for securing the absorbent article about the waist of the wearer. The illustrated versions of the diaper (30) comprise such fasteners (82). In at least one version, the fasteners (82) are situated in the rear region (34) of the diaper (30), and located inboard each longitudinal extending side edge (46). The fasteners (82) may be configured to encircle the hips of the wearer and engage the backsheet (38) of the front region (32) of the diaper (30) for holding the diaper (30) on the wearer. Desirably, the fasteners (82) are releasably engageable directly with the garment facing surface of the backsheet (38). Desirably, the fasteners (82) comprise a mechanical fastening system. Alternatively, the diaper (30) may comprise a fastening panel (68) situated in the front region (32) of the garment facing surface of the backsheet (38). In such a configuration, the fasteners (82) are releasably engageable with the fastening panel (68) to maintain the diaper (30) about the waist of the wearer. Such an arrangement provides the ability to vary the size of the waist opening in very small increments over a wide range to fit the waist of the wearer. The fasteners (82) may have a variety of shapes and sizes which provide the desired fastening of the diaper (30) about the waist of the wearer.

Desirably, the first fastener component and cooperating fastener component comprise complementary elements of a cooperatively interengaging mechanical fastening system. The mechanical fastener components can be provided by mechanical-type fasteners such as hooks and the like, which comprise cooperating and complementary mechanically interlocking components.

As shown in FIGS. 1 and 2, for example, the mechanical fastening system may be a hook-and-loop type of fastening system. Such fastening systems typically comprise engagement members having the form of a “hook” or hook-like male component and comprise a cooperating “loop” or loop-like female component, which engages and releasably interconnects with the hook component. Desirably, the interconnection is selectively releasable and re-attachable. Conventional systems are, for example, available under the VELCRO trademark.

A configuration which employs a selectively releasable, inter-engaging mechanical fastening system can, for example, locate the first fastener component on the ear (89), and can locate the cooperating, second fastener component on the fastening panel (68). For example, with the representatively shown hook-and-loop fastener, the fastening component, which is attached to the ear (89), may comprise a hook type of mechanical engagement element and the complementary fastening component is the fastening panel (68) which can comprise a loop type of fastening element.

It should also be readily apparent that, in the various configurations of the invention, the relative positions and/or materials of the first fastening component and its cooperating, complementary fastening component can be transposed.

Examples of traditional hook-and-loop fastening systems and components are described in U.S. Pat. No. 5,019,073 issued to Roessler et al, the entire disclosure of which is hereby incorporated by reference in a manner that is consistent herewith. Other examples of hook-and-loop fastening systems are described in U.S. Pat. Nos. 5,605,735 and 6,030,373 issued to VanGompel et al.; the entire disclosures of which are hereby incorporated by reference in a manner that is consistent herewith.

The loop material can comprise a nonwoven, woven, or knit fabric. For example, a suitable loop material fabric can be composed of a 2 bar, warp knit fabric of the type available from Guilford Mills, Inc., Greensboro, N.C. under the trade designation #34285, as well as other types of knit fabrics. Suitable loop materials are also available from the 3M Company, which has distributed a nylon woven loop under their SCOTCHMATE brand. The 3M Company has also distributed a linerless loop web with adhesive on the backside of the web and 3M knitted loop tape.

The loop material may also comprise a nonwoven fabric having continuous bonded areas defining a plurality of discrete unbonded areas. The fibers or filaments within the discrete unbonded areas of the fabric are dimensionally stabilized by the continuous bonded areas that encircle or surround each unbonded area, such that no support or backing layer of film or adhesive is required. The unbonded areas are specifically designed to afford spaces between fibers or filaments within the unbonded area that remain sufficiently open or large to receive and engage hook elements of the complementary hook material. In particular, a pattern-unbonded nonwoven fabric or web may comprise a spunbond nonwoven web formed of single component or multi-component melt-spun filaments. At least one surface of the nonwoven fabric can comprise a plurality of discrete, unbonded areas surrounded or encircled by continuous bonded areas. The continuous bonded areas dimensionally stabilize the fibers or filaments forming the nonwoven web by bonding or fusing together the portions of the fibers or filaments that extend outside of the unbonded areas into the bonded areas, while leaving the fibers or filaments within the unbonded areas substantially free of bonding or fusing. The degree of bonding or fusing within the bonding areas desirably is sufficient to render the nonwoven web non-fibrous within the bonded areas, leaving the fibers or filaments within the unbonded areas to act as “loops” for receiving and engaging hook elements. Examples of unmodified, suitable point-unbonded fabrics are described in U.S. Pat. No. 5,858,515, issued to Stokes et al., the entire disclosure of which is incorporated herein by reference in a manner that is consistent herewith.

As used herein, the term “spunbond web” refers to a web formed by extruding a molten thermoplastic material as filaments from a plurality of fine, usually circular, capillaries with the diameter of the extruded filaments then being rapidly reduced, for example, by fluid-drawing or other well known spunbonding mechanisms. The production of spunbond nonwoven webs is illustrated in U.S. Pat. No. 4,340,563, issued to Appel, et al., the entire disclosure of which is incorporated herein by reference in a manner that is consistent herewith.

The loop material need not be limited to a discrete or isolated patch on the outward surface of the article. Instead, the loop material can be provided by a substantially continuous, outer fibrous layer which is assembled, integrated or otherwise joined to extend over a predetermined surface area of the desired article. For example, the outer fibrous layer may be arranged to extend over substantially the total exposed surface area of a cloth-like outer cover employed with the article. Further, the outer cover can comprise an outer nonwoven layer that functions as a cooperating fastener component.

The engagement force between the selected first fastener component and its appointed and cooperating second fastener component should be large enough and durable enough to provide an adequate securement of the article on the wearer during use. In particular arrangements, especially where there are sufficiently high levels of engagement shear force provided by the fastening system, the fastening engagement may provide a peel force value of not less than a minimum of about 40 grams-force (gmf) per inch of the “width” of engagement between the first and second fastener components. In further arrangements, the fastening engagement may provide a peel force value of not less than about 100 gmf/inch to provide improved advantages. In desired configurations, the fastening engagement may provide a peel force value of not less than about 200 gmf per inch of the “width” of engagement between the first and second fastener components. Alternatively, the peel force is not less than about 300 gmf/inch, and optionally is not less than about 400 gmf/inch to further provide improved benefits. In other aspects, the peel force is not more than about 1,200 gmf/inch. Alternatively, the peel force is not more than about 800 gmf/inch, and optionally is not more than about 600 gmf/inch to provide improved performance.

The engagement force between the selected first fastener component and its appointed and cooperating second fastener component may additionally provide a shear force value of not less than about 400 gmf per square inch of the area of engagement between the first and second fastener components. Alternatively, the shear force is not less than about 1,000 gmf/in², and optionally, is not less than about 1,700 gmf/in². In further aspects, the shear force can be up to about 4,400 gmf/in², or more. Alternatively, the shear force is not more than about 3,900 gmf/in², and optionally is not more than about 3,500 gmf/in² to provide improved performance.

Depending upon the specific design and end use, the engagement force between a given male component and a given female component may be adjustable. This adjustability may allow for an enhanced engagement force during wear and a reduced engagement force during removal. The adjustability of engagement force may be linked to an amount that a hook material has been stretched. For example, the engagement force may be increased or reduced for a stretched hook material compared to the same hook material in an unstretched condition.

When comparing engagement force between stretched hook materials, forces must be normalized to an unstretched condition. For example, by stretching a hook material 25%, the number of hooks per square inch is reduced to 0.8 times (1/[(100+25)/100])=0.8) the number of hooks as compared to the unstretched hook material. This reduction in hooks per square inch will reduce the engagement force per square inch by 0.8 times, but will demonstrate equivalent normalized engagement force as measured by the included test method. Additionally, comparisons are made by joining hook material in a stretched state to loop material and then testing for engagement force, as compared to joining hook and loop material and then stretching. It is believed that physical manipulation of a joined hook and loop system may vary the engagement force.

An increase in engagement force may be desired in a stretched state. For example, when a caregiver dons a product on a child very loosely (in a minimally stretched condition) a first level of engagement force is desired. However, if the caregiver dons the same product on the same child more tightly (in a highly stretched condition) for example immediately before play time, an increased level of engagement is desired.

Alternatively, a decrease in engagement force may be desired in a stretched state. Many caregivers remove the product by pulling or elongating the hook material as they remove the product from the user. In these conditions, it may be advantageous for the hook to reduce engagement force as the caregiver is removing or elongating the hook material. In this situation a “high” level of engagement is attained during use, and a relatively “lower” level of engagement is attained during removal. This allows for easier removal, as well as less damage to the loop material for a given level of in use engagement force.

Fastening systems may include a female component and a male component having a plurality of hook elements. The male component may be adapted for releasable engagement with the female component. Further, the fastening system may have a first normalized peak shear force to disengage the female component from the male component when the male component is stretched 0%. The fastening system may have a second normalized peak shear force to disengage the female component from the male component when the male component is stretched 10%. The first normalized peak shear force may be at least 10% greater than the second normalized peak shear force. Alternatively, the first normalized peak shear force may be at least 20% greater than the second normalized peak shear force. Alternatively, the first normalized peak shear force may be at least 33% greater than the second normalized peak shear force. The engagement force in this fastening system decreases as the male component is stretched.

A portion of the male component of the fastening system may be stretchable at least 10% when loaded at 250 g/in. Alternatively, a portion of the male component of the fastening system may be stretchable at least 15% when loaded at 250 g/in. A portion of the male component of the fastening system may be elastic.

FIGS. 3A and B illustrate a prophetic example of a first hook material that displays a reduction in engagement force upon stretching. FIG. 3A illustrates a side view of a first hook material in an unstretched condition, and FIG. 3B illustrates a side view of the hook material of FIG. 3A after stretching. The hook material illustrated in FIG. 3A includes a plurality of hook elements having have a stem (80) and a cap (82). Further, the cap defines a characteristic cap angle (84). The cap angle (84) is the smallest angle a tangent to the bottom side of the cap (82) makes to perpendicular. The average cap angle (84) is the average of all the cap angles (84) of the individual hooks that make up the hook material. Theoretically a smaller cap angle (84) provides greater engagement force. FIG. 3A illustrates a hook material in an unstretched (0%) state, having a first average cap angle. FIG. 3B illustrates a hook material in a stretched (for example 10%) state, having a second average cap angle. The second average cap angle (84) is greater than the first average cap angle (84). This theoretical hook material would have a greater normalized peak shear force in the unstretched state than in the stretched state.

Many different designs may be utilized to achieve a reduction in engagement force and or an increase in cap angle (84). The cap angle (84) may be increased by designing the hook material such that when a stretching force is applied, the force is transferred to the individual hooks, which in turn deform. The deformation of the hooks may be tailored, for example, by only deforming a fraction of the hooks in the hook material, or by changing the amount of deformation the hooks undergo upon a given amount of stretching of the hook material. This change may be effected by the choice of materials, the specific thickness of the materials, the physical structure of the individual hooks, and further by the composition or structure of the base or support material.

FIGS. 3A and B illustrate a side view of a first hook material in an unstretched condition and a stretched condition. One method by which the material stretches is by deformation of the hook elements. The hook elements, and more specifically, the caps (82) open, thereby creating a lower engagement force. FIGS. 4A and B illustrate a side view of a second hook material in an unstretched condition and a stretched condition. This material demonstrates a second design where the hook elements may deform when the material is stretched. The hook elements, and more specifically, the caps (82) open, thereby creating a lower engagement force.

The hook material may be designed such that the average cap angle (84) of the material after stretching 10% may be at least 20 degrees greater than the average cap angle when the material is unstretched. Alternatively, the hook material may be designed such that the average cap angle (84) of the material after stretching 10% may be at least 40 degrees greater than the average cap angle when the material is unstretched.

The fastening system may be designed such that the normalized peak shear force of the unstretched material may be at least 10% greater than the normalized peak shear force of the material after stretching 10%. Alternatively, the fastening system may be designed such that the normalized peak shear force of the unstretched material may be at least 25% greater than the normalized peak shear force of the material after stretching 10%.

An increase in engagement force may be desired in a stretched state, for example, in situations where the caregiver anticipates a need for a higher or lower amount of engagement force. FIGS. 5A and 6A illustrate examples of hook material in an unstretched state, where stretching may increase the engagement force by a decrease in cap angle (84). FIGS. 5A and 6A illustrate a male component of a fastening system including a plurality of hook elements. The male component may be adapted for releasable engagement with a female component of the fastening system. The fastening system may have a first normalized peak shear force to disengage the female component from the male component when the male component is stretched 0%. The fastening system may have a second normalized peak shear force to disengage the female component from the male component when the male component is stretched 10%. The first normalized peak shear force may be at least 10% less than the second normalized peak shear force. Further, depending upon the desired end use, the first normalized peak shear force may be at least 20% less than the second normalized peak shear force.

FIGS. 5A and B illustrate a prophetic example of a first hook material that displays an increase in engagement force upon stretching. FIG. 5A illustrates a side view of a first hook material in an unstretched condition, and FIG. 5B illustrates a side view of the hook material of FIG. 5A after stretching. The hook material illustrated in FIG. 5A includes a plurality of hook elements having a stem (80) and a cap (82). Further, the cap defines a characteristic cap angle (84). FIG. 5A illustrates a hook material in an unstretched (0%) state, having a first average cap angle. FIG. 5B illustrates a hook material in a stretched (for example 10%) state, having a second average cap angle. The second average cap angle (84) is less than the first average cap angle (84). This theoretical hook material would have a greater normalized peak shear force in the stretched state than in the unstretched state.

Many different designs may be utilized to achieve an increase in engagement force and or a decrease in cap angle (84). The cap angle (84) may be decreased by designing the hook material such that when a stretching force is applied, the force is transferred to the individual hooks, which in turn, deforms the individual hooks. The deformation of the hooks may be tailored, for example, by only deforming a fraction of the hooks in the hook material, or by changing the amount of deformation the hooks undergo upon a given amount of stretching of the hook material. This change may be effected by the choice of materials, the specific thickness of the materials, the physical structure of the individual hooks, and further by the composition or structure of the base or support material.

FIGS. 5A and B illustrate a side view of a first hook material in an unstretched condition and a stretched condition. One method by which the material stretches, is by deformation of the hook elements. The hook elements, and more specifically, the caps (82) may be reoriented to capture and hold loop material more securely, thereby creating a higher engagement force. FIGS. 6A and B illustrate a side view of a second hook material in an unstretched condition and a stretched condition. This material demonstrates a second design where the hooks elements may deform when the material is stretched. The hook elements, and more specifically the caps (82) are reoriented to capture and hold loop material more securely, thereby creating a greater engagement force.

The hook material may be designed such that the average cap angle of the material after stretching 10% may be at least 20 degrees less than the average cap angle when the material is unstretched. Alternatively, the hook material may be designed such that the average cap angle of the material after stretching 10% may be at least 40 degrees less than the average cap angle when the material is unstretched. The average cap angle (84) may be at least 90 degrees when the material is unstretched.

The shear strength of a mechanical fastening system can be determined in accordance with the following method.

Test Method: Shear Strength

Test Procedure

This procedure is a tensile bench test to measure the shear force required to separate a mechanical fastening system that joins two materials. The shear force of separation is measured by determining load values as the two materials are pulled apart parallel to their plane of contact. The shear strength test values are an indication of how well the mechanical fastening system stays engaged against in-plane shear force. The sample is pulled in the tensile tester until the sample pulls apart. Shear strength is the peak load result. Shear strength may be normalized by dividing the peak load by the contact area at 0% stretch resulting in a force per normalized area.

1. Overview

A material sample of two material layers joined by a mechanical fastening system such as a hook and loop system is assembled. The fastening system joins two pieces of material that overlap in the landing area. The sample is prepared by aligning and applying the loop material to the stabilized hook material, and by rolling a 4.5 lb. (2.04 kg) mechanical roller over the fastening system to engage the fastener. The sample is then placed between clamps on a tensile tester. One piece of material is held in the upper clamp, while the other is held in the lower clamp. The fastening system is arrayed between the clamps, approximately parallel to the edges of the clamp faces. The width of the hook material is 13 mm, the width of the loop material is approximately 64 mm, and the hook overlaps the loop 50 mm in the lengthwise direction (at 0% stretch). The gauge length is 3 inches (76 mm) between the edges of the clamp faces. The term “load” refers to the gram value measured by the load cells in the tensile tester.

The jaws are separated at a controlled rate of 12 inch/min (305 mm/min) until the fastening system is pulled apart. The load values generated on the material throughout this process are recorded. The load as a function of elongation is recorded on a computer.

Load values for samples of non-standard widths and lengths should be normalized by multiplying or dividing by the factor by which the sample overlap area deviates from 13 mm by 50 mm. For example, the peak load value derived by pulling apart a 1 inch (25.4 mm) wide by 50 mm long sample should be multiplied by 13/25.4.

Suitable materials comprise hook and loop fastening systems, which may comprise or be attached to materials used to form the disposable garments described herein.

2. Apparatus and Materials

-   -   2.1 Constant Rate of Extension (CRE) tensile tester such as an         MTS tensile tester model Sintech 1/G; available from MTS Systems         Corporation, located at 1400 Technology Drive, Eden Prairie,         Minn., USA.     -   2.2 Load cells: A suitable cell selected so the majority of the         peak load values fall between 10% and 90% of the manufacturer's         recommended ranges of load cell's full scale value; for example,         Model 100N available from MTS Systems Corporation, located at         1400 Technology Drive, Eden Prairie, Minn., USA.     -   2.3 Operating software and data acquisition system such as MTS         TestWorks® for Windows software version 3.10; available from MTS         Systems Corporation, located at 1400 Technology Drive, Eden         Prairie, Minn., USA.     -   2.4 Grips: pneumatic-action grips, top and bottom, identified as         part number 38.00716 available from MTS Systems Corporation.         -   2.5 Grip faces: 25 by 75-mm (1 by 3-inch) interlocking faces             such as are available from MTS Systems Corporation.     -   2.6 Roller: 4.5 lb (2.04 kg) mechanical roller available from         Chemsultants International, Mentor, Ohio, USA.         -   2.7 Plexiglas, ¼″×4″×4″

3. Conditioning

Reasonable ambient conditions are required for testing. The instruments used should be calibrated as described in the manufacturer's instructions for each instrument.

4. Test Specimen (Illustrated in FIG. 5)

The hook material sample (102) having an unstretched width of 13 mm and an unstretched length of 50 mm is adhered to a piece of rigid material, for example a piece of Plexiglas (110). The material may be adhered to the Plexiglas in an unstretched state, such that the dimensions of the hook material are 13 mm by 50 mm. Alternatively, the material may be adhered to the Plexiglas in a stretched state, for example such that the dimensions of the hook material are 13 mm by 55 mm (stretched 10%). This method normalizes the attachment strengths for the stretch of the material. When testing material samples taken from absorbent articles, the dimensions of the hook material (102) and the loop material (101) may be adjusted. Results should be normalized for the size of overlap tested.

The loop material sample (101) is cut to have a width (a) of approximately 2.5 in. (64 mm) and a length (b) of approximately 4 in. (102 mm). The loop sample (101) is placed onto the hook material sample (102) such that the loop material sample (101) completely overlaps (c) the hook material sample (102), perpendicular from the 64 mm wide edge, centered on the 64 mm. The joined materials should not be handled or pressed.

The specimen is placed on a hard flat surface, and the test sample is then pressed down with a standard 4.5 lb (2.04 kg) mechanical roller by rolling the roller across the hook/loop engagement area back and forth in the length direction on the loop material sample (101) one time. The centerline of the sample should be aligned with the centerline of the face of the roller.

The specimen is tested using the tensile test procedure that follows. At least four specimens of each sample should be tested, and the results averaged.

5. Procedure

Tensile Tester Test Conditions

Preload No Test speed 305 mm/min Gauge length (h): 3 inches (76 mm) Number of cycles: 1

-   -   A. Using the tensile frame pushbutton controls for crosshead         position, move grips to provide a gauge length (h) of 3 inches         (76 mm). Tare the crosshead channel to this initial gauge         length.     -   B. Without touching the fastening area, hold a material specimen         so that the hook material is up and the loop material is down.         Place the Plexiglas onto which the hook is adhered in the upper         jaw (103) of the tester. Place the hook material in the upper         jaw (103) such that it is centered in the horizontal direction,         with the loop material extending below the center of the upper         jaw (103).     -   C. Close the upper jaw (103) on the specimen and tare the load         channel.     -   D. Hold the specimen in such a way as to minimize slack in the         specimen, but do not place the specimen under tension, and close         the lower jaw (104) on the loop material.     -   E. Run the test using the above parameters by clicking on the         RUN button.     -   F. When the test is complete, save the data to a sample file.     -   G. Remove the specimen from the jaws (103, 104).     -   H. Run additional specimens of a given sample using steps B-G;         the data for all specimens should be saved to a single file.     -   I. Continue testing all samples in this manner.     -   J. Data are reported as the peak load and the total energy under         the load-extension curve.

Having described the invention in rather full detail, it will be readily apparent that various changes and modifications can be made without departing from the spirit of the invention. All of such changes and modifications are contemplated as being within the scope of the invention as defined by the subjoined claims. 

1. A fastening system suitable for incorporation into a disposable absorbent article, the fastening system comprising: a female component; and a male component having a plurality of hook elements adapted for releasable engagement with the female component, wherein the fastening system has a first normalized peak shear force to disengage the female component from the male component when the male component is stretched 0%, the fastening system has a second normalized peak shear force to disengage the female component from the male component when the male component is stretched 10%, the first normalized peak shear force being at least 10% greater than the second normalized peak shear force.
 2. The fastening system of claim 1, wherein the first normalized peak shear force is at least 20% greater than the second normalized peak shear force.
 3. The fastening system of claim 1, wherein at least a portion of the male component is stretchable at least 10% when loaded at 250 g/in.
 4. The fastening system of claim 1, wherein at least a portion of the male component is stretchable at least 15% when loaded at 250 g/in.
 5. The fastening system of claim 1, wherein at least a portion of the male component is elastic.
 6. A fastening system suitable for incorporation into a disposable absorbent article, the fastening system comprising: a female component; and a male component having a plurality of hook elements adapted for releasable engagement with the female component, wherein at least a portion of the plurality of hook elements have a stem and a cap, the cap defining a cap angle; wherein the fastening system has a first normalized peak shear force to disengage the female component from the male component and a first average cap angle when the male component is stretched 0%, the fastening system has a second normalized peak shear force to disengage the female component from the male component and a second average cap angle when the male component is stretched 10%, the first normalized peak shear force being greater than the second normalized peak shear force, and the second average cap angle being greater than the first average cap angle.
 7. The fastening system of claim 6, wherein the second average cap angle is at least 20 degrees greater than the first average cap angle.
 8. The fastening system of claim 6, wherein the second average cap angle is at least 90 degrees.
 9. The fastening system of claim 6, wherein the first normalized peak shear force is at least 10% greater than the second normalized peak shear force.
 10. The fastening system of claim 6, wherein at least a portion of the male component is stretchable at least 10% when loaded at 250 g/in.
 11. The fastening system of claim 6, wherein at least a portion of the male component is stretchable at least 15% when loaded at 250 g/in.
 12. The fastening system of claim 6, wherein at least a portion of the male component is elastic.
 13. A fastening system suitable for incorporation into a disposable absorbent article, the fastening system comprising: a female component; and a male component having a plurality of hook elements adapted for releasable engagement with the female component, wherein the fastening system has a first normalized peak shear force to disengage the female component from the male component when the male component is stretched 0%, the fastening system has a second normalized peak shear force to disengage the female component from the male component when the male component is stretched 10%, the first normalized peak shear force being at least 10% less than the second normalized peak shear force.
 14. The fastening system of claim 13, wherein the first normalized peak shear force is at least 20% less than the second normalized peak shear force.
 15. The fastening system of claim 13, wherein at least a portion of the male component is stretchable at least 10% when loaded at 250 g/in.
 16. The fastening system of claim 13, wherein at least a portion of the male component is stretchable at least 15% when loaded at 250 g/in.
 17. The fastening system of claim 13, wherein at least a portion of the male component is elastic.
 18. A fastening system suitable for incorporation into a disposable absorbent article, the fastening system comprising: a female component; and a male component having a plurality of hook elements adapted for releasable engagement with the female component, wherein at least a portion of the plurality of hook elements have a stem and a cap, the cap defining a cap angle, wherein the fastening system has a first normalized peak shear force to disengage the female component from the male component and a first average cap angle when the male component is stretched 0%, the fastening system has a second normalized peak shear force to disengage the female component from the male component and a second average cap angle when the male component is stretched 10%, the first normalized peak shear force being less than the second normalized peak shear force, and the second average cap angle being less than the first average cap angle.
 19. The fastening system of claim 18, wherein the second average cap angle is at least 20 degrees less than the first average cap angle.
 20. The fastening system of claim 18, wherein the first average cap angle is at least 90 degrees.
 21. The fastening system of claim 18, wherein the first normalized peak shear force is at least 10% less than the second normalized peak shear force.
 22. The fastening system of claim 18, wherein at least a portion of the male component is stretchable at least 10% when loaded at 250 g/in.
 23. The fastening system of claim 18, wherein at least a portion of the male component is stretchable at least 15% when loaded at 250 g/in.
 24. The fastening system of claim 18, wherein at least a portion of the male component is elastic. 